Applied Physiology

lymph

Location: Interstitial fluid is found between cells, Lymph is located within lymphatic vessels and lymphatic tissue.

1. Drains excess interstitial fluid
2. Transports dietary lipids from gastrointestinal tract to the blood
3. Protects against invastion through immune responses.

is a specialized form of reticular connective tissue that sontains large numbers of lymphocytes

agranular white blood cells

1. B cells
2. Tcells

1. Drains excess interstitial fluid (fluid balance)
2. Immunity
3. transports lipids from digestive tract to systemic veins

1&2 most important

• closed-ended microscopic lymphatic vessel that begins in spaces between cells and converges with other lymphatic capillaries to form lymphatic vessels
• Weave between tissue cells & blood capillaries in loose connective tissue
• Highly permeable: Large molecules, proteins, to large to enter blood capillaries, easily pass into lymphatic capillaries
• Structure: Overlapping endothelial cell, creates "flaplike" minivalve. Collagen filamentsanchor endothelial cells, ↑ in IF, valves open

alarge vessel that collects lymph from lymphatic capillaries and converges with other lymphatic vessels to form the thoracic and right lymphatic ducts

Lymph: essentially recycled blood plasma

Excess Ifluid exits arterial ends of capillary beds

Most IF reabsorbed at venous ends

Primary function of lymph system: Accessory route for the extra =3 liters of filtered plasma

Drain fairly large area of the body

• Major paired: Lumbar, Bronchomediastinal, Subclavian, Juglar
• single: Intestinal

• Lymph capillaries
• lymph vessels
• lymph trunks
• lymph ducts
• subclavian veins 

• 2 large:
• Right lymphatic: drains right upper quadrant into R subclavian
• Thoracic: drains majority from body into L subclavian
• lymph returned to systemic blood before entering heart

• Lymphangitis: severely inflamed, vessels of vasa vasorum become congested with blood
• Lymphedema: short-term but severe localized edema

•Lymphatic Pump – it’s all about the pressures

–Lymphokinesis: movement of lymph

–1-way SL valves, open & close from extrinsic & intrinsic pressures

–Extrinsic:

•Skeletal muscle contractions: how most lymph is moved

–Muscle contractions create pressure gradient, lymph moves forward

•Inspiration: 

–Intra-abdominal pressure ↑ intra-thoracic pressure ↓ creates pressure gradient in thoracic duct, lymph flows upward

–Intrinsic:

•Pressure w/in lymphangion from smooth muscle contraction

lymphangion: functional unit of lymph vessel, lies between two SL valves

Lymphoid cells: immune system cells, combined with "supporting" cells form scaffolding of lymphoid tissue 

• lymphocytes: main warriors, arise in red bone marrow mature into; Tcells (directly attack virus-infected & tumor cels) or Bcells ( produce antibodies/immunohlobins)
• Macrophages: function as phagocytes & active T lympocytes
• Dendritic cells: capture antigens & taken to nodes. Also activate T lymphocytes 
• Reticulat cells: fibroblast-like cells, produce storms, network supports other cell types in lymphoid tissue

• House & provide proliferation site for lymphocytes
• Cycling of lymphocytes ensures reach infected or damaged sites
• Ideal surveillance site for lympocytes & macrophages
• composed largely of loose connective Reticulat tissue
• Diffuse lymphoid tissues: in nearly every body organ
• Lymphoid follicles: part of larger lymphoid organs or aggregations 

2 basic functions to protect body:

• Filtration: macrophages in nodes remove & destroy microorganisms, prevents entering blood & spreading throughout body
• Immune system activation: strategic location of nodes provides lymphocytes easy access to antigens

•Nodes vary in size & shape, most bean shaped, <2.5 cm in length

•Surrounded by fibrous capsule of connective tissue

•Trabeculae extends inside, divides node into compartments

•Stroma, internal framework, support lymphocytes

•Two regions:

•Cortex: 

•Superficial houses B cells

•Deep houses T cells

•Medulla: 

•Medullary cords: both B & T cells

•Lymph sinuses: lymph capil

→Lymph enters node thru afferent vessels

→Slowly moves through medullary sinuses, allows lymphocytes & macrophages to work

Exits node via efferent vessels

→Lymph passes through several nodes before completely cleansed

•Buboes/swollen glands: large numbers of bacteria trapped in node, becomes inflamed, swollen, tender to touch

•Most common bacterial infections:

•Bacterial: strep throat, tonsillitis

•Viral: mononucleosis

•Disease of middle ages: buboes are characteristic symptom of bubonic plague “Black Death”

Cancer-infiltrated lymph nodes

•Secondary cancer sites, metastasized cells enter lymphatic system

•Nodes are not usually painful, but swollen, helps distinguish infection

• Cancer cells & infections can spread along lymphatics to nodes & other organs
  • >85% of lymph from breast enters axillary lymph nodes
  • Remainder enters parasternal nodes
• Cutaneous lymphatic plexus
  • Diffuse network of lymphatics areola of nipple, drain lymph from skin & breast surface area•
• Subareolar plexus (plexus of Sappey)
  • Located under areola, drain secretory tissue & ducts of breast through communication between cutaneous plexus & large lymphatics

• Breast Cancer: one of most common forms of malignancy in women
  • Axillary nodes contact with “axillary tail” (tail of Spence)
    • Cancer or infection may spread, leads to enlargement of other axillary nodes, are “seeded” with malignant or  bacteria infected cells
    • Note: Interpectoral nodes often metastasized
  • Sentinel lymph node (SLN):  first node to which cancer can spread through lymphatic system, biopsy reveals if cancer metastasized
• Mastectomy: surgical removal of one or both breasts, partial or complete
  • Because cancer cells can easily spread through lymphatic system associated with breast, lymphatic vessels & nodes sometimes removed
• •Mastitis: breast infections

• Largest lymphoid organ
• ≈ size of fist, left side of abdominal cavity beneath diaphragm
• Site for lymphocyte proliferation & immune surveillance & response
• Key point: blood-cleansing functions:
  • Extracts aged & defective blood cells & platelets
  • Macrophages remove debris & foreign matter
  • 3 supportive functions:
    • 1.Stores hemoglobin for later use
    • 2.Stores platelets & monocytes for later use
    • 3.Fetal erythrocyte production

White pulp

Primary role, creates lymphocytes

Red pulp

Composed of platelets, granulocytes, RBCs & plasma

Filters antigens, microorganisms & defective/worn out RBCs

• Primary organ of lymphatic system
  • Pinkish gray in childhood
  • Yellows with age, fat replaces lymphoid tissue
  • Bi-lobed subdivided into lobules
  • Vital role in immunity
  • Before birth, source of lymphocytes (B, T & NK cells)
  • Shortly after birth:
    • Thymus secretes thymosin & other regulators
    • Enables lymphocytes to divide & mature into into T cells
    • Cells tested, ≈5% pass & become part of immune system defense

• MALT: set of distributed lymphoid tissues located in mucous membranes throughout body
  • Tonsils: lymphoid ring, protects nasal & oral cavities, serve as “first line of defense” against infections
    • Composed of: palatine (2 pairs), pharyngeal/adenoids, lingual, tubal (2 pairs)
    • Tonsillar crypts: trap & destroy bacteria
• Peyer’s patches: aggregated lymphoid nodules in ileum
  • Destroy bacteria, can’t enter peritoneum; generate “memory“ lymphocytes
• Appendix: tubular offshoot of colon, high concentrations of lymphoid follicles
  • Destroy bacteria before breach intestinal wall
  • Generate “memory” lymphocytes

• Lymphoma: occurs when B or T lymphocytes have abnormal division or life, develop in lymph nodes, spleen, bone marrow, unknown etiology
  • Latest 2008 WHO lymphoma classification, largely abandoned "Hodgkin" vs. "Non-Hodgkin" grouping
  • Instead, lists over 80 different forms of lymphomas in 4 broad groups